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题库 / OG2016-CR-53
Humans get Lyme disease from infected ticks. Ticks get infected by feeding on animals with Lyme disease, but the ease of transmission from host animal to tick varies. With most species of host animal, transmission of Lyme disease to ticks is extremely rare, but white-footed mice are an exception, readily passing Lyme disease to ticks. And white-footed mouse populations greatly expand, becoming the main food source for ticks, in areas where biodiversity is in decline.
The information in the passage most strongly supports which of the following?
In areas where many humans are infected with Lyme disease, the proportion of ticks infected with Lyme disease is especially high.
Very few animals that live in areas where there are no white-footed mice are infected with Lyme disease.
Humans are less at risk of contracting Lyme disease in areas where biodiversity is high.
Ticks feed on white-footed mice only when other host species are not available to them.
The greater the biodiversity of an area, the more likely any given host animal in that area is to pass Lyme disease to ticks.
情景：人类从被感染的虱子上得莱姆病。虱子是因为有莱姆病的动物而被感染的，但是从动物身上传染给虱子的困难度是不同的。白脚老鼠很容易被传染莱姆病。白脚老鼠在生物多样化降低的地区正在扩张。
推理：由于推理文段中没有结论，所以本题为演绎推理。
选题方式：略
选项分析：
A选项：在那些很多人类感染莱姆病的地方，感染莱姆病的虱子的比率是非常高的。文段中只说过“人类从被感染的虱子上得莱姆病”，并没有提到这两者呈严格正比关系。
B选项：很少有住在没有白脚老鼠地方的动物被感染莱姆病。文段中只讲过白脚老鼠最容易传染病，并没有说过其它动物不能传染。
C选项： Correct. 在生物多样性高的地方，人类不容易感染莱姆病。因为白脚老鼠在生物多样性少的地方繁殖的好，所以人类在生物多样性多的地方自然会更不容易感染莱姆病。
D选项：只有在没有其它寄主的时候，虱子才会寄生在白脚老鼠身上。本选项讨论的是虱子的喜好，文段中没有提过。
E选项：生物多样性越多的地方，寄主越有可能把莱姆病传染给虱子。文段中没有提过本选项。
题目里边涉及了一个动态关联关系，关系的两头是生物多样性和人类得病，所以言下之意就是人类得病和生物多样性之间有一定的联系，选项要涉及到这个关系的两头才算完整。
biodiversity下降-->mouse增多-->infected ticks增多-->人容易被传染
A 从”人“到ticks，不完整
B 其他动物怎样怎样，无关
C 从”biodiversity“到”人“，完整
D ticks和mouse，不完整
E 所有的宿主，无关
contract: If you contract a serious illness, you become ill with it.
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